Such nozzle protection eliminates deformation of the vessel shell and serves to receive forces necessary to remove the so-called slag tups. From past experience we know that slag tups on Thomas, LD and LDAC converters are inevitable. The annular segments are either welded or cast. The annular segments, mostly consisting of hematite iron have great surface hardness resulting from cooling of the scale. They tend less to stick to the discharge resulting from the metallurgic process than those nozzle rings that are made of welding steel. Deposits of slag and/or metal spray which may still occur can generally be removed with pneumatic hammers or special hooks which do not cause any major damage to the ring segments. If there is any damage to the nozzle rings, usually only one segment is affected which may then be replaced independently.
A nozzle ring having cooling water passages or ducts has already been suggested (DT-AS 1 302 880) for protection of the vessel nozzle. This known nozzle ring has a hook-shaped profile, whereby one portion, radially directed inward, forms a part of the frontal face of the nozzle, and the other portion is adapted to the slant of the vessel wall, both portions being arranged at a distance from the vessel wall to form an air gap between themselves and the vessel wall. The disadvantage of this arrangement is that the water cooling is located directly in the converter nozzle. The slag tups are separated from the cooling medium only by the wall thickness of the ring with the cooling medium passages. Loosening of the slag tups may lead to leaking, caused by puncture, of the ring containing the cooling medium. This danger is sufficient to prohibit practical use of the known ring containing cooling water passages. Leakage of cooling water at the superheated nozzle area of a metallurgic vessel, from which waste gases escape, would inevitably lead to explosions in the flue gas stack and/or vessel itself.
In today's technology, it has only been established to protect the vessel shell in the nozzle area from excessive thermal stress caused by heat radiation. The present invention, however, provides a forced-cooled protective nozzle where, on one hand, the advantages of ring segments which can be subjected to great mechanical stress, can be exploited and where, on the other hand, the disadvantage of rings with cooling water passages which are threatened by mechanical stress, can be avoided.
The invention solves this by providing a solid supporting ring which carries the annular segments and which is indirectly connected to the vessel shell; a tubular annular shield connected with the supporting ring forming a hollow space around the vessel shell, with water passages arranged within, which are firmly connected to the annular shield, and which however, do not have any attachment to the vessel shell; the supporting ring having an externally protruding rim next to the connection with the annular shield and the rim being fitted with means of attaching the annular segments, such means of attachment being accessible from the exterior.
Starting with the advantages of the annular segments, the advantages of the invention consist of a larger bearing surface made possible by the supporting ring, furthermore in the tubular annular shield which constitutes a quasi "double hood" for the conical portion of a converter. The protected bottom of this annular shield is used to accommodate the cooling water pipes. While the slag tups form smaller deposits on the enlarged annular segments and can be removed more easily, there is no danger of damaging pipes carrying cooling water from mechanical stress on the annular segments. The protective nozzle of the invention is therefore more durable under extreme conditions than the one known heretofore. The invention does, however, also increase safety during operation: despite all safety measures pipes carrying cooling water may leak and even during inverted position of the vessel its contents may only drip into the trough formed by vessel shell and annular shield. In the upright position of the vessel the leaking water runs over the vessel shell as far as it does not evaporate. In this manner the protective nozzle according to the invention guarantees safe operation by keeping any risk to a minimum.
The hollow space containing the pipes carrying cooling water most likely decreases in most instances, due to the pressure on the vessel shell caused by exchange of the masonry, until the vessel shell rests on the pipes. The rounded shape of the pipes, however, makes them strong enough so that expansion of the annular shield is more likely. One improvement on the invention provides the cooling water pipes with half-profile or semi-cylindrical cross sections, the cross sectional edges adhering to the bottom of the annular shield, thus forming a seal. Another improvement on the invention is that supporting ring and annular shield are connected by a welding seam, with one of the pipes circulating cooling water arranged in this area.